Oxygen reduction on silver catalysts electrodeposited on various nanocarbon supports

Abstract

In this work, Ag particles were electrodeposited onto nitrogen-doped graphene oxide, graphene, multi-walled carbon nanotube (MWCNT), and Vulcan carbon XC-72R supports by varying the upper potential limit. The surface morphology of the resulting Ag-based catalysts was examined by scanning electron microscopy. The electrochemical oxygen reduction reaction (ORR) was tested in alkaline media employing the rotating disk electrode method. The variation of the upper potential limit influenced the size of silver nanoparticles and their number density on the substrate surface. All the Ag-based electrocatalysts studied in this work showed remarkable ORR activity in terms of half-wave potentials. The ORR results combined with hydrogen peroxide reduction results prove that all Ag catalysts tested are suitable for both reactions. Ag/NGO2 catalyst possesses the highest mass activity for ORR, which indicates a relationship between the Ag loading and electrocatalytic activity. The electroreduction of oxygen on all the electrodeposited silver catalysts follows a four-electron pathway in alkaline environment. These materials are promising alternatives for Pt/C catalyst to be used as alkaline membrane fuel cell cathodes.

Silver Nanowire‐Based Catalysts for Oxygen Reduction Reaction in Alkaline Solution

“…We obtained comparable MA values to those reported in the literature. [38,48] For example, in our recent article, where silver was electrodeposited onto four different carbon substrates, the MA values at 0.8 V were similar when compared to the results obtained in this work. [38] Also, the MA values at 0.85 V in a study by Cai et al, where the ORR was tested on Ag catalysts prepared by rapid precipitation-reduction synthesis, were close to those of this work.…”

“…Similar values of E 1/2 were obtained in other recent works. [21,[36][37][38] The Koutecky-Levich (K-L) equation was used to determine the ORR kinetic parameters. The number of electrons transferred per O 2 molecule (n) was calculated from RDE data using the K-L equation [Eq.…”

“…Similar Tafel slope values have been obtained in earlier studies. [17][18][19][20]38,43,46] Taking into account observations by Blizanac et al, the Tafel slope values for the Ag(110) were constantly changing between À 80 and À 120 mV dec À 1 , and for the Ag(111) and Ag(100) at higher overpotentials the slope values for Ag(hkl) were close to À 120 and À 130 mV dec À 1 and at lower overpotentials close to À 70 and À 80 mV dec À 1 . [7] These Tafel slope values suggest that the first electron transfer to the O 2 molecule is the rate-determining step in the overall ORR process.…”

In Silico High-Throughput Screening of Ag-Based Electrocatalysts for Anion-Exchange Membrane Fuel Cells

“…We further calculated the theoretical dissolution potentials ( U ) of the alloys to estimate the stability of the catalytic surface under the working conditions. In fact, it has been suggested that the main factor for catalyst degradation is the dissolution of the catalyst in PEMFC. , In AEMFCs, which improve the catalyst stability by lowing the operating potential through the use of alkaline electrolytes, it was also reported that the dissolution of Ag still occurs. , The theoretical dissolution potential ( U ) of the alloys was calculated to estimate the electrochemical stability of the catalytic surface under the working conditions, as given by equation . where U Ag 0 is the dissolution potential of pure Ag under standard conditions and E alloy , E subsurf , and μ Ag are the energies of the alloy surface with a pure Ag skin, the energy of the surface after complete surface layer dissolution, and the chemical potential of the pure bulk Ag, respectively. N surf is the number of surface atoms, and n is the number of electrons transferred during dissolution.…”

“…45,46 In AEMFCs, which improve the catalyst stability by lowing the operating potential through the use of alkaline electrolytes, it was also reported that the dissolution of Ag still occurs. 33,47 The theoretical dissolution potential (U) of the alloys was calculated to estimate the electrochemical stability of the catalytic surface under the working conditions, 48 as given by equation 11.…”